AFP/ New Delhi

The youngest convict in an infamous fatal gang-rape on a bus in New Delhi three years ago has been released from a youth correctional facility, Indian police said Sunday.

"The convict was handed over to an NGO. He is no longer under the jurisdiction of the police," Delhi police spokesman Rajan Bhagat told AFP.

"He has been given a new identity and his criminal record has been expunged," a police source added.

News of the release was immediately condemned by the parents of the victim, a medical student who died of her injuries in a Singapore hospital nearly two weeks after the attack on December 16, 2012.

"Our fight was all about this convict not being allowed to walk free. If he has come out, what is the point of the hearing at the Supreme Court?" the mother of the victim told reporters.

"We want justice for our daughter."

India media said the 20-year-old convict, who cannot be named for legal reasons, had been handed over to a charitable organisation on Sunday but police sources said the move had actually taken place some days ago.

The name of the NGO has not been released over fears that their offices could be attacked.

News of the release came only hours before a hearing on Monday at India's Supreme Court where a women's rights group will file a petition against the release.

The parents and women's rights groups have been opposing the release of the youngest attacker, mainly on the grounds that it was unclear if he had been rehabilitated and was ready to be reintegrated into society.

The attacker was the youngest of a group of men who brutally assaulted the 23-year-old student on a bus, triggering global outrage and protests in India over the country's high levels of violence against women.

He was sent to a correctional home for three years under India's juvenile laws while four others were convicted and given the death penalty in 2014. Their appeals against hanging are pending in the Supreme Court.

The student, who succumbed to her injuries two weeks after the attack, was publicly named by her mother on the third anniversary of her death last week, in an effort to end the stigma facing sex attack victims in India.

Under Indian law, the victim of a sex attack cannot be named even after their death.